IMessageManager assistance

Could use a little assistance if someone can help really quick. I wrote a class file that ties into IBackgroundTask and IMessageManager so that every day at 1am, a method runs that checks the database for certain values and then sends out an email to certain
users on my system. All of this works perfectly when sending to my own account which is configured for the Admin user on the system, however, every other user takes this error in the log files.

which makes me think that it's trying to find every user on the local domain's mail server instead of sending out to Gmail or Yahoo or wherever the user's email account is located. Here is how I'm generating the email

I'm thinking I'm missing something from one of these two calls that instructs the Orchard Messaging agent to send the emails externally instead of just to the local email server. Is that correct? And if so, can someone let me know what needs to be added
to either one to get that to work?

You were right...it was "sort" of in the mail server configuration. I have to authorize using the full email address, not just the username. So I had to use admin@myrealitypicks.com as the username, not just admin. I wish my mail server had sent back a more
descriptive error message. Had it simply said username invalid, I would have known to go straight there and check that setting. Note to self: next time test with an external email address. Thanks Bertrand!